1. Field of the Invention
The invention relates to a process for preparing lactose with a lowered reproducible, stable pH and a lower ash level.
2. Prior Art
Lactose or milk sugar is obtained by crystallization from a milk derived source, such as cheese whey. Whey, the byproduct of cheese manufacture, is available in about 3.5 billion gallons per year. Numerous attempts have been made to extract the valuable protein and lactose components from the whey. In one method, whey protein is concentrated by passing the whey through an ultrafiltration membrane. The protein retentate is dried and the lactose and ash rich permeate is further treated to remove the lactose therefrom. Lactose prepared by crystallization from permeate varies in pH from 6.4 to 7.7, and the ash content is generally in excess of 0.12% by weight depending on the level in raw batch material (milk). Impurities in the lactose magma after crystallization, centrifugation and packaging influence the final product pH. Consistency in the maintenance of the lactose pH at not greater than 7.44, but preferably 7.0 or less is essential to customers due to the current requirements for lactose pH imposed by the United States government and other countries.
It has now been found that the pH and the ash content of lactose, produced by various membrane process techniques and particularly the ultrafiltration of whey, can be controlled in accordance with the present invention.